This invention relates to hydraulic retarder systems and more particularly to the filling apparatus for such systems.
Hydraulic retarders are generally utilized on large vehicles to assist in vehicle braking or deceleration. Retarders are particularly useful when operating on a downgrade thereby relieving the vehicle brakes of extended usage.
When the retarder is initially activated, a large supply of pressurized fluid must be delivered to the retarder such that filling thereof will occur. Since it would not be economical to provide a hydraulic pump of sufficient displacement to accomplish the initial filling of the system, the prior art systems have utilized a pressurized accumulator.
As is well-known, an accumulator can supply a large amount of oil during short periods of time. While these systems provide for rapid filling of the retarder without significantly increasing the size of the pump, they do, however, require physical space within the transmission. If a spring-loaded accumulator is used, additional space for the compressed spring volume is required. If a gas or oil accumulator is used, intermittent checking of the pressure of the gas charge is required. The gas charge also requires some additional space in addition to the accumulator. The prior art accumulators also require a hydraulic connection with the high pressure circuit of the pump, and a control mechanism to ensure that the proper pressure level is maintained.
It has also been suggested in U.S. patent application Ser. No. 822,841, filed July 7, 1986, and assigned to the assignee of the present application, that an eductor can be used to draw oil from the oil reservoir or sump of the vehicle transmission when oil is delivered from the system pump through the input nozzle to the eductor throat. The eductor is operable, therefore, to add oil to the pump delivered oil.